Title

Author

Degree

Doctor of Philosophy (PhD)

Department

Oceanography & Coastal Sciences

Document Type

Dissertation

Abstract

Sediment transport over Sandy Point dredge pit in the northern Gulf of Mexico was examined using field measurements and a finely resolved numerical model. Delft3D model with well-vetted computational grid and input parameters was used. Numerical experiments were performed to examine the effect of wind-generated waves, wind-driven currents and their interaction on sediment dynamics in our study area during a cold front in November 2014 and fair-weather conditions between July and August of 2015. Sediment dispersal from the lower Mississippi River, sediment resuspension, transport and deposition with high spatial and temporal resolution were simulated. A reliable satellite-derived near-surface suspended particulate matter (SPM) map was employed to provide an initial condition in a numerical model and support the model calibration/verification. To prepare SPM maps, short-wave infrared (SWIR) and near-infrared atmospheric correction algorithms on remote sensing reflectance (Rrs) products from Landsat-8 OLI and Management Unit of the North Sea Mathematical Models (MUMM) and SWIR.NIR atmospheric correction algorithms on Rrs products from MODIS-Aqua were evaluated. Results indicated that SWIR atmospheric correction algorithm was the suitable algorithm for Landsat-8 OLI and SWIR.NIR atmospheric correction algorithm outperformed MUMM algorithm for MODIS. Delft3D Flow, wave and sediment transport were validated using LSU WAVCIS (Wave-Current-Surge Information System) and NDBC (National Data Buoy Center) data for both events. Results suggested that the primary source of sediment for the Sandy Point dredge pit during a cold front was re-suspension due to the fortified bottom shear stress (BSS) by wind-induced waves and currents. Strong southward wind-driven currents during the cold front passage dispersed sediments from the Mississippi River passes and inhibited riverine sediment supply from the Sandy Point dredge pit. Results also showed that total cold front passages in a year (30-40 passages per year) contribute to the sedimentation thickness over Sandy Point dredge pit from 16% to 24% of the total sedimentation thickness annually. Results indicated that during the fair-weather event, Mississippi River plays a pivotal role in providing sediment for Sandy Point dredge pit and about 60% of deposited sediments are from the Mississippi River plume.